In an LTE-A system, the transmission of uplink control information (UCI) in a PUSCH (Physical Uplink Shared Channel) should take multi-carrier transmission and MIMO (Multiple Input Multiple Output) transmission into consideration. To obtain the most diversity gains, it is necessary to repeatedly transmit ACK and RI on all transmission layers and take high load caused by multi-carrier into account at the same time. Single-code word and single-layer transmission is only supported in current standards and ACK/NACK and/or RI are transmitted in a small amount. How to repeatedly transmit ACK/NACK and/or RI (Rank Indicator) on multi-code word and multi-layer and code channels should be further clarified.
Uplink control information including ACK/NACK feedback information, periodical/non-periodical channel state information (CSI) (including CQI (Channel Quality Indicator) information/PMI (Precoding Matrix Indicator) and RI information). In an LTE R8 system, UCI can be transmitted on a PUCCH (Physical Uplink Control Channel) or transmitted multiplexing with the data on a PUSCH.
Non-periodical reporting of CQI/PMI/RI information is transmitted on a PUSCH. For the condition that the number of CQI/PMI/RI feedback bits is no more than 11, a RM (32, O) block code is adopted for coding the transmitting data during channel coding firstly and then corresponding transmission resource sizes of CQI/PMI/RI are switched over through repetition/truncation coding, wherein, O refers to the number of bits of the original input information, and the RM (32, O) block code in an LTE Rel-8 system can support 11-bit original input information at most; for the condition that the number of CQI/PMI/RI feedback bits is greater than 11, a tail-biting convolutional code is adopted for coding channels. While periodical reporting of CQI/PMI/RI information is transmitted on PUCCH format 2/2a/2b channels in accordance with the preconfigured reporting cycle, and a RM (20, A) block code is adopted for coding channels of the transmission data, wherein, A means the number of bits of the original input information, and the RM (20, A) block code in an LTE Rel-8 system can support 13-bit original input information at most.
ACK/NACK feedback information can be transmitted on a PUCCH or PUSCH according to specific dispatching. 4-bit ACK/NACK information is supported at most in a Rel-8 system. When ACK/NACK information is transmitted in PUCCH format1/1a/1b, channel coding will not be performed; when ACK/NACK information is transmitted multiplexing with the data on the PUSCH, 1-bit or 2-bit ACK/NACK information is coded repeatedly as a channel code. The channel code of more than 2-bit ACK/NACK information, is as same as the channel code of non-periodic CQI/PMI/RI transmission, combining a RM (32, O) block code and repetition/truncation code.
To be compatible with an LTE system, an LTE-A system supports the transmission of UCI on a PUCCH and/or PUSCH. LTE-A can support 5 carriers at most to aggregate at present, that is to say, in the same uplink subframe, UE should feed back multi-bit UCI corresponding to a plurality of downlink subframes. Taking ACK/NACK feedback information as an example, it is necessary for a FDD system to feed back 10-bit ACK/NACK information at most and for a TDD system to feed back 40-bit ACK/NACK information at most. To support the transmission on a PUSCH with more information bits, the current LTE channel coding mode should be extended. In the LTE system, when selecting a channel coding mode of CQI, it has verified that the RM (Reed-Muller) block code has more better performance, the coding and decoding are simple, and it is unnecessary to define a code word set separately for the input information with different lengths. Compared with a RM code, a convolutional code has a poor performance, especially when the original information with a short length is input. However, for the LTE-A system, when a receiving terminal adopts maximum likelihood (ML) for coding, exponential growth will exist between the decoding complexity of a RM code and the length of coding original information. For a convolutional code, Viterbi decoding algorithm is used as the optimal ML decoding algorithm, and linear growth will exist between decoding complexity and the length of coding original information. Therefore, in the LTE-A, UCI should select a channel coding mode with moderate performance and decoding complexity in accordance with the size of information bits.
On the other hand, it is necessary to support four-layer spatial multiplexing transmission of two code words at most in LTE-A. How to transmit UCI on a plurality of layers should also be resolved. As shown in the conclusion of the meeting at present, CQI is multiplexed in a code word, while ACK/NACK and/or RI are transmitted repeatedly on all code words to obtain diversity gains. For ACK/NACK and/or RI transmission, the number of symbols occupied on each layer is calculated as per the following formula and current standards are expanded to a certain degree:
      Q    ′    =      min    ⁢          {                        [                                    O              ·                              M                sc                                  PUSCH                  -                  initial                                            ·                              N                symb                                  PUSCH                  -                  initial                                            ·                              β                offset                PUSCH                                                                                      ∑                                      r                    =                    0                                                                              C                                              (                        0                        )                                                              -                    1                                                  ⁢                                                                  ⁢                                  K                  r                                      (                    0                    )                                                              +                                                ∑                                      r                    =                    0                                                                              C                                              (                        1                        )                                                              -                    1                                                  ⁢                                                                  ⁢                                  K                  r                                      (                    1                    )                                                                                ]                ,                  4          ·                      M            sc            PUSCH                              }      
Thus channel coding output bit of ACK/NACK and/or RI, QACK is equal to Q′*Qm. How to determine βoffsetPUSCH is unconcluded. The same value can be used for all code words or different values are adopted for different code words or even for different layers, at this time the number of UCI symbols obtained of each code word/layer will be different. Different data modulation methods may be used for each code word/layer, thus how to repeat information bits and conduct channel coding and modulation on different code words should be standardized.
Two technologies can support multi-code word and multi-layer UCI transmission at present.
FIG. 1 is a schematic diagram of UCI transmission of independent coding of each code word. As shown in Scheme I of FIG. 1, channel coding for UCI of each code word is performed independently, and then channel interleaving, scrambling and modulation are conducted for UCI and data. During channel coding, the code word is repeated according to the mapped layers and modulation methods, so as to ensure that the information transmitted on a plurality of the mapped layers is the same.
FIG. 2 is a schematic diagram of UCI transmission of independent coding of each layer. As shown in Scheme II of FIG. 2, firstly layer mapping is performed for the data and CQI to obtain data bits of each layer and UCI is processed on each layer independently (the process is the same as the one conducted in accordance with current standards), then UCI and the data are merged. Different number of information bits or information symbol can be used on each layer.
As for Scheme I, repetition in a code word is conducted after channel coding and a modulation method is required, thus coding is complicated; as for Scheme II, channel coding, interleaving, scrambling, modulation and other processes are performed on each layer independently, thus processing complexity is increased (it is only necessary for a code word to undergo this process as shown in Scheme I). The disadvantage of the two schemes means that no high information bit load (for example, information source of greater than 11 bits) is supported for the reused R8 coding mode.